Neutron Cross Section Measurement In The Protodune-Sp Experiment

Understanding the detector response to neutrons will be critical for performing neutrino oscillation analyses in the next-generation Deep Underground Neutrino Experiment (DUNE). The DUNE physics program is centered around measuring the neutrino flavor composition as a function of their energy both at the near and the far detector. Neutrinos in the DUNE beam will have energies ranging between 100 MeV and 10 GeV, which is significant, because individual neutrino energies will not be known beforehand and will have to be reconstructed. Neutrino interactions in DUNE will produce leptons and hadrons – including protons, pions, and neutrons. Neutrons can transport energy away from their origin and sometimes go undetected. In addition to the primary neutrons produced by the neutrino, subsequent interactions of the charged hadrons can result in secondary neutrons. Neutrons are a source of missing energy and will bias the neutrino energy measurement. Currently, there is also a 20% energy scale uncertainty and a 40% uncertainty on the energy resolution for neutrons in DUNE, which must be addressed. ProtoDUNE Single-Phase (ProtoDUNE-SP) is a 770-ton prototype for the DUNE far detector and was designed to both validate the technology that will be employed in DUNE and to measure cross sections for the charged hadrons (pions, protons, and kaons) at the relevant energies for DUNE. The ProtoDUNE-SP experiment, therefore, is in a unique position to characterize the secondary neutron component for DUNE. This is achieved by searching for candidate neutron interactions in ProtoDUNE-SP events and using these to facilitate a measurement of the neutron inelastic cross section as well as an estimate of the neutron energy and number. The cross section measurement presented here is based on neutrons produced in 1 GeV, π+ events captured in 2018 by ProtoDUNE-SP in accordance with the production and cross section models in theGEANT4 simulation toolkit, version 4.10.6p1. The best-fit neutron inelastic cross section, in the kinetic energy range of 114 to 314 MeV, is 1.24(+0.10)(−0.08) (stat. ⊕ syst.) barns.